Use Raymott's male friend. ;-)
That is, if you need to specify, as in:
A: Doesn't your husband object to you having so many female friends?
B: Why should he? We both have male and female friends. Marriage doesn't mean you have to stop seeing friends just because they're the opposite sex.
However, we often don't need to specify. A friend's sex is often of as little signifiance as their sexuality, religion, politics, etc.
In a language where nouns have gender, then we automatically know that the masculine noun, for example,
Freund in German refers to a male friend, and that the feminine noun
Freundin refers to a female friend. However, this does not necessarily mean that there is any focus on the natural sex of the person rather than the grammatical gender of the noun. There is no evidence to suggest that Germans think of a table as a male thing or a newspaper as a female thing just because of the grammatical gender of the words that refer to these things.
The natural sex of the friend referred to is normally clear from the context, as in "I bumped into an old friend yesterday,
He was in town on business and ...", or the name: "I had dinner last week with
Peter, a friend from college days". If the natural sex of the friend is of interest, and is not clear from other signs, then clarification will be requested/provided:
A: Fancy coming to the pub tonight?
B: I can't, I'm afraid. Pat's invited me round for a meal.
A: Who's Pat?
B: A friend I used to work with.
A: Boyfriend?
B: {
No, just someone I've known since my time at Sainsbury's. [sex still not clear and, presumably, unimportant.]
B: {
No, he's gay, but we both enjoy cooking, and ... . [sex now clear, though not necessarily important.]
B: {
No, Patricia - you remember Pat from Sainsburys, don't you?) [sex now clear, though not necessarily important.]